(i) Field of the Invention
This invention relates to a method for producing a silicon nitride layer on a substrate by a chemical vapor deposition (CVD) process utilizing a plasma chemical reaction, and more particularly to a technology which is applied for producing a coating of an optical fiber, a stabilized film for a semiconductor device and a gate insulation film for IG-FET etc.
(ii) Description of the Prior Art
Conventionally, a silicon nitride layer is produced in such a manner that silane (SiH.sub.4) and ammonia (NH.sub.3) are reacted by a plasma chemical vapor deposition utilizing a glow discharging to prepare the layer on a substrate of about 200.degree. to 400.degree. C.
Thus formed silicon nitride layer has odd electric charges due to presence of unpaired couplings of silicon atoms or of silicon clusters which are produced by silane in the layer. Because of the presence of the odd charges, layers made by the conventional process have been found insufficient for a final coating of MOS, IC and so on. In particular, in case of the semiconductor device memory, there has been a demand of such a silicon nitride layer as will make the ultraviolet rays having a wave length of 254 nm (applied for writing of EP ROM) pass therethrough without influencing the stabilized layer.